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1.
Using anchors made of fibre reinforced polymers (FRP) is an increasingly accepted method to delay the delamination of FRP sheets from the concrete surface and to enhance the capacity of FRP strengthened concrete structures. For many applications, FRP anchors are primarily loaded in shear. When used for seismic retrofitting schemes, the anchors are subjected to cyclic loads which may lead to premature fatigue failure. To date, however, shear strength of FRP anchors has experienced much less attention than their tension resistance. This paper documents tests on isolated FRP anchors which were conducted to determine the seismic shear capacity of FRP anchors and to propose design rules. To this end, a test setup was developed which allows direct and reverse loading of FRP anchors.  相似文献   
2.
A tracked vehicle has been widely used in exploring unknown environments and military fields. In current methods for suiting soil conditions, soil parameters need to be given and the traction performance cannot always be satisfied on soft soil. To solve the problem, it is essential to estimate track-soil parameters in real-time. Therefore, a detailed mathematical model is proposed for the first time. Furthermore, a novel algorithm which is composed of Kalman filter (KF) and improved strong tracking filter (STF) is developed for online track-soil estimation and named as KF–ISTF. By this method, the KF is used to estimate slip parameters, and the ISTF is used to estimate motion states. Then the key soil parameters can be estimated by using a suitable soil model. The experimental results show that equipped with the estimation algorithm, the proposed model can be used to estimate the track-soil parameters, and make the traction performance satisfied with soil conditions.  相似文献   
3.
Energy literacy, which encompasses broad content knowledge as well as affective and behavioral characteristics, will empower people to make appropriate energy-related choices and embrace changes in the way we harness and consume energy. Energy literacy was measured with a written questionnaire completed by 3708 secondary students in New York State, USA. Results indicate that students are concerned about energy problems (affective subscale mean 73% of the maximum attainable score), yet relatively low cognitive (42% correct) and behavioral (65% of the maximum) scores suggest that students may lack the knowledge and skills they need to effectively contribute toward solutions. High school (HS) students scored significantly better than middle school (MS) students on the cognitive subscale; gains were greatest on topics included in NY State educational standards, and less on topics related to “practical” energy knowledge such as ways to save energy. Despite knowledge gains, there was a significant drop in energy conservation behavior between the MS and HS students. Intercorrelations between groups of questions indicate energy-related behaviors are more strongly related to affect than to knowledge. These findings underscore the need for education that improves energy literacy by impacting student attitudes, values and behaviors, as well as broad content knowledge.  相似文献   
4.
This paper presents a theoretical study of Biot flow–induced damping in saturated soil during shear wave excitations. The solid skeleton is treated as equivalent linear. Biot flow–induced damping is evaluated for the cases of resonant column tests and site response analysis, based on the spectral response of a soil column/layer under harmonic torsional/horizontal excitations. Closed-form analytical solutions indicate that Biot flow–induced damping is hydraulic conductivity and frequency dependant. At the first resonance in a resonant column test, Biot flow–induced damping is dependent on a dimensionless hydraulic conductivity parameter K. For K within the range of 0.01 to 100, corresponding to coarse sands and clean gravels, Biot flow–induced damping may have an important contribution to total soil damping, especially at small strain levels. For site response analysis, Biot flow–induced damping should be considered for coarse sands and clean gravels, but can be practically neglected for fine sands, silts, and clays. The effects of soil porosity, mass coupling, and non-Poiseuille flow on Biot flow–induced damping are discussed.  相似文献   
5.
In this project the use of natural media filtration (NMF) was evaluated for its ability to remove colloidal particles from the aqueous phase as a function of ionic strength and filter media type by determining first-order kinetic deposition rate coefficients. Mushroom compost (MC) and leaf compost (LC) were tested as natural filter media and the results were compared to those obtained using sand and granular activated carbon (GAC). The highest deposition rate coefficients were observed for GAC, followed by LC and MC, and the lowest deposition rate coefficients were found for sand. As predicted by the Derjaguin–Landau–Verwey–Overbeek theory, higher deposition rates were obtained at higher solution ionic strengths. Overall the experiments suggest that the NMF process can efficiently remove colloidal particles from surface waters.  相似文献   
6.
The purpose of this research was to study the effect of surfactant structure and micelle composition on the partitioning of sparingly soluble organic compounds (SSOCs) into surfactant micelles. The surfactants used in this research were sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DDTMA), tetradecyl trimethyl ammonium bromide (TDTMA), hexadecyl trimethyl ammonium bromide (HDTMA), Mega-9 (nonanoyl-n-methyl glucamide) and polyoxyethylene ether (POE). The SSOCs used were toluene, trichloroethylene and p-xylene. SSOC partitioning into the micelles of cationic surfactants increased with increasing number of carbon atoms in the surfactant tail. However, when the amount of partitioned SSOC was normalized by the length of the straight-chain tail, there was no difference in SSOC removal between SDS, DDTMA, TDTMA, and HDTMA. Using these data and previously published data, correlations were developed between the normalized partition coefficient and hydrophobicity for both cationic and anionic straight chain surfactants. Mixed surfactant systems had lower CMCs and lower partition coefficients than did single surfactants in the 1–10 mM concentration range. The presence of a mixture of SSOCs did not affect SSOC partitioning into micelles in this study.  相似文献   
7.
Fractographic examinations were carried out on the fracture surfaces of both single-edge notched bend (SENB) and wedge-loaded compact tension (WLCT) specimens of S2 freshwater ice. Formvar solutions provided an effective means of making replicas that revealed various patterns of the fracture surfaces. The fracture modes consisted of both cleavage and brittle intergranular fracture, with cleavage fracture dominating. The cleavage planes of the S2 ice were mainly the {0 0 0 1} and {10¯1 1} planes under the experimental conditions for this study. Kinks forming new grain boundaries were found on the fracture surfaces of polycrystalline S2 ice for the first time. Kinking is regarded as a possible mechanism of plastic deformation for polycrystalline ice and to partially account for the high fracture energy of S2 ice found in this study.  相似文献   
8.
This paper provides the results of two small-scale testing programs linked to large-scale field programs carried out by the writers and others. The large-scale in-situ sea ice testing program was part of the Office of Naval Research's (ONR's) Sea Ice Mechanics Initiative (SIMI). Three field trips to Barrow, Alaska, were completed to examine the seasonal evolution of the first-year sea ice growing on Elson Lagoon. Trips were made in November, March, and May, when significant changes in thickness and temperature profile were evident. The experiments were designed to determine the fracture behavior of sea ice in situ and make comparisons with small-scale lab tests. Due to the unique microstructure of the sea ice tested, it was necessary to complete small-scale (0.1 m) tests for comparative purposes. A detailed study of the ice fabric at the site revealed a very strong alignment of the c-axis. This prompted a study of the fracture properties parallel (hard-fail) and perpendicular (easy-fail) to the preferred c-axes orientation plane in both the largeand small-scale tests. The effects of c-axis alignment, temperature and microstructure on the fracture toughness and tensile strength are investigated.  相似文献   
9.
A model is developed for simulating oil spills that initially behave as jets or plumes. The model is based on the Lagrangian integral method. The model can simulate a liquid (oil) in an ambient (seawater), or an oil∕gas mixture in seawater. The model considers both shear and forced entrainment. The jet∕plume model is combined with two additional models for oil transport in the intermediate field and the far-field to provide complete simulations of the oil transport and fate. The model can take into account the stratified ambient conditions. 3D unsteady ambient current conditions can be used in the simulations. The model is used to simulate the field experiments conducted by the Institut for Kontinentalsxkkel Undersokelser in the North Sea in 1996 and 1997 and compare with the field data. A scenario simulation using the model is presented to demonstrate the model capability.  相似文献   
10.
Concerns surrounding the continued, un-checked use of petroleum-based fuels in the transportation sector, the search for more sustainable, renewable alternatives, and the constraints of the existing supply infrastructure in the United States have placed a spotlight on biomass-derived fuels. The central question of the ethanol debate has changed from “Should we make ethanol?” to “From what should we make ethanol?” emphasizing the importance of understanding the differences between specific biomass supply systems for fuel ethanol. When presented with numerous options, the priorities of an individual decision maker will define which feedstock alternative is the most appropriate choice for development from their perspective. This paper demonstrates how energy data can be successfully used to quantify assessment metrics beyond a standard net energy value calculation, thus quantifying the relative “value” of ethanol supply systems. This value is defined based on decision-maker priorities that were adopted from national energy policy priorities: increased national energy security and increased conservation of energy resources. Nine energy assessment metrics that quantify detailed system energy data are calculated and a straightforward comparative assessment is performed between corn and corn stover feedstocks produced under the same farm scenario. Corn stover is shown to be more compatible with the national energy policy priorities and it is recommended that additional research be performed on utilizing this feedstock from the corn farm.  相似文献   
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